The present invention generally relates to tilting bed carriers. More specifically, the invention is directed to the art of tilting bed carriers using a tilting platform having a low center of gravity and relatively small loading angle.
Various carriers, including car carriers as well as industrial carriers (for carrying forklifts, tractors and machines, etc.), are known, as shown in U.S. Pat. No. 4,750,856 ('856 patent) to Lapiolahti and U.S. Pat. No. 5,061,147 ('147 patent) to Nespor. These patents disclose a bed carrier or tiltable platform mounted on a truck chassis which moves from a horizontal position on the truck frame to a tilted position in which the rear end of the bed or platform engages the ground. The tiltable platform of the '856 patent is attached to the frame of a truck chassis, and a hydraulic cylinder tilts the platform rearwardly from the horizontal position to an inclined position by simultaneous upward and rearward movement of the front end of the bed and downward and rearward movement of the rear end of the bed, to enable the loading of a disabled vehicle. The carrier platform of the '147 patent is situated on a subframe with parallel beams that, in a generally similar fashion, support independent sliding and tilting movement of the platform.
Carriers, such as those disclosed in the '856 and '147 patents, utilize a tiltable platform with main longitudinal rails or beams mounted above the truck frame of a dual rear wheel chassis. Conventional commercial truck chassis have been equipped with dual rear wheels in single and tandem axle configurations. Recently, another truck chassis rear wheel configuration has been developed and commercialized, known as a “Super Single” wheel and tire system. The Super Single wheel system employs one wide wheel and tire on each end of a truck axle, as compared to two narrow wheels and tires on each end of dual-wheeled truck axle. Each style of wheel configuration has advantages and disadvantages. The Super Single wheel configuration is less expensive and provides better fuel economy than dual rear wheel configurations. Dual rear wheel configurations provide redundancy in the event of a single flat tire.
Dual rear-wheeled chassis have approximately 7 inches of clear space between the tires and the truck frame, whereas the Super Single wheel configuration provides about 12 inches of such clearance. It was discovered that using a Super Single wheel configuration which provides this additional 5 inches of space between the rear wheels and truck frame, together with the use of air bag rear suspensions, enables the location of a carrier's longitudinal slide or platform beams beside the truck frame, and adjacent the rear wheels. This lowers the subframe and sliding platform about 6 inches relative to the top of the truck frame, as compared to conventional carriers.
Lowering the subframe and sliding platform about 6 inches has several advantages compared to conventional carriers with slide beams located above the truck frame. Typical commercial truck chassis have truck frame heights ranging from 36-44 inches relative to the ground, depending on the size of the truck frame and the type of rear suspension used. Traditional carriers have deck heights about 12-13 inches above the truck frame, which equates to conventional deck heights of about 48-57 inches above the ground. A lower tiltable platform height translates into a lower center of gravity, since the deck height relative to the ground is now in the range of about 42-51 inches, which provides improved truck handling. More available payload height is also provided. A lower platform height also means that the tiltable platform will have a lower load angle relative to the ground, which can facilitate loading (e.g., a large counterweight on a forklift can be more easily loaded, etc.).